3. Oral; not written. Nuncupative will/testament, a will or testament made by word of mouth only, before witnesses, as by a soldier or seaman, and depending on oral testimony for proof.
[from Blackstone]

'Nuncupative' found in Matthew Hughes' story, "The Gist Hunter," in
the June F&SF (um, yeah, I'm a bit behind in my reading). In the story it
seems to be used in the second sense above, which appears to have been obsolete
even in 1913, and that meaning is not even mentioned in current dictionaries. Is
there anyone who will understand this word when they read it without
having to look it up? Heh.